Sema: Shave another 8 bytes off of Constraint

Author: slavapestov

include/swift/Sema/Constraint.h

@@ -336,6 +336,7 @@ class Constraint final : public llvm::ilist_node<Constraint>,
     private llvm::TrailingObjects<Constraint,
                                   TypeVariableType *,
                                   ConstraintFix *,
+                                  DeclContext *,
                                   ContextualTypeInfo,
                                   OverloadChoice> {
   friend TrailingObjects;
@@ -354,6 +355,9 @@ class Constraint final : public llvm::ilist_node<Constraint>,
   /// Whether we have a tail-allocated fix.
   unsigned HasFix : 1;
 
+  /// Whether we have a tail-allocated DeclContext.
+  unsigned HasDeclContext : 1;
+
   /// Whether the \c Restriction field is valid.
   unsigned HasRestriction : 1;
 
@@ -392,7 +396,7 @@ class Constraint final : public llvm::ilist_node<Constraint>,
   /// node is unused.
   unsigned isDiscarded : 1;
 
-  // 23 bits remaining
+  // 22 bits remaining
 
   union {
     struct {
@@ -425,20 +429,14 @@ class Constraint final : public llvm::ilist_node<Constraint>,
         /// Used for ValueWitness constraints.
         ValueDecl *Ref;
       } Member;
-
-      /// The DC in which the use appears.
-      DeclContext *UseDC;
     } Member;
 
     /// The set of constraints for a disjunction.
     ArrayRef<Constraint *> Nested;
 
     struct {
-      /// The first type
+      /// The first type.
       Type First;
-
-      /// The DC in which the use appears.
-      DeclContext *UseDC;
     } Overload;
 
     struct {
@@ -454,8 +452,6 @@ class Constraint final : public llvm::ilist_node<Constraint>,
       /// The type being called, primarily a function type, but could
       /// be a metatype, a tuple or a nominal type.
       Type Callee;
-      /// The declaration context in which the application appears.
-      DeclContext *UseDC;
     } Apply;
   };
 
@@ -531,6 +527,10 @@ class Constraint final : public llvm::ilist_node<Constraint>,
     return HasFix ? 1 : 0;
   }
 
+  size_t numTrailingObjects(OverloadToken<DeclContext *>) const {
+    return HasDeclContext ? 1 : 0;
+  }
+
   size_t numTrailingObjects(OverloadToken<ContextualTypeInfo>) const {
     return Kind == ConstraintKind::SyntacticElement ? 1 : 0;
   }
@@ -876,20 +876,6 @@ class Constraint final : public llvm::ilist_node<Constraint>,
     return *getTrailingObjects<OverloadChoice>();
   }
 
-  /// Retrieve the DC in which the overload was used.
-  DeclContext *getOverloadUseDC() const {
-    assert(Kind == ConstraintKind::BindOverload);
-    return Overload.UseDC;
-  }
-
-  /// Retrieve the DC in which the member was used.
-  DeclContext *getMemberUseDC() const {
-    assert(Kind == ConstraintKind::ValueMember ||
-           Kind == ConstraintKind::UnresolvedValueMember ||
-           Kind == ConstraintKind::ValueWitness);
-    return Member.UseDC;
-  }
-
   FunctionType *getAppliedFunctionType() const {
     assert(Kind == ConstraintKind::ApplicableFunction);
     return Apply.AppliedFn;
@@ -900,11 +886,6 @@ class Constraint final : public llvm::ilist_node<Constraint>,
     return Apply.Callee;
   }
 
-  DeclContext *getApplicationDC() const {
-    assert(Kind == ConstraintKind::ApplicableFunction);
-    return Apply.UseDC;
-  }
-
   ASTNode getSyntacticElement() const {
     assert(Kind == ConstraintKind::SyntacticElement);
     return SyntacticElement.Element;
@@ -920,6 +901,12 @@ class Constraint final : public llvm::ilist_node<Constraint>,
     return isDiscarded;
   }
 
+  /// Retrieve the DC in which the overload was used.
+  DeclContext *getDeclContext() const {
+    assert(HasDeclContext);
+    return *getTrailingObjects<DeclContext *>();
+  }
+
   /// For an applicable function constraint, retrieve the trailing closure
   /// matching rule.
   std::optional<TrailingClosureMatching> getTrailingClosureMatching() const;

lib/Sema/CSSimplify.cpp

@@ -13089,7 +13089,7 @@ bool ConstraintSystem::simplifyAppliedOverloadsImpl(
         // Determine the type that this choice will have.
         Type choiceType = getEffectiveOverloadType(
             constraint->getLocator(), choice, /*allowMembers=*/true,
-            constraint->getOverloadUseDC());
+            constraint->getDeclContext());
         if (!choiceType) {
           hasUnhandledConstraints = true;
           return true;
@@ -16335,7 +16335,7 @@ ConstraintSystem::simplifyConstraint(const Constraint &constraint) {
     return simplifyApplicableFnConstraint(
         constraint.getAppliedFunctionType(), constraint.getCalleeType(),
         constraint.getTrailingClosureMatching(),
-        constraint.getApplicationDC(), /*flags=*/std::nullopt,
+        constraint.getDeclContext(), /*flags=*/std::nullopt,
         constraint.getLocator());
 
   case ConstraintKind::DynamicCallableApplicableFunction:
@@ -16382,7 +16382,7 @@ ConstraintSystem::simplifyConstraint(const Constraint &constraint) {
 
     resolveOverload(constraint.getLocator(), constraint.getFirstType(),
                     constraint.getOverloadChoice(),
-                    constraint.getOverloadUseDC());
+                    constraint.getDeclContext());
     return SolutionKind::Solved;
 
   case ConstraintKind::SubclassOf:
@@ -16429,7 +16429,7 @@ ConstraintSystem::simplifyConstraint(const Constraint &constraint) {
   case ConstraintKind::UnresolvedValueMember:
     return simplifyMemberConstraint(
         constraint.getKind(), constraint.getFirstType(), constraint.getMember(),
-        constraint.getSecondType(), constraint.getMemberUseDC(),
+        constraint.getSecondType(), constraint.getDeclContext(),
         constraint.getFunctionRefInfo(),
         /*outerAlternatives=*/{},
         /*flags*/ std::nullopt, constraint.getLocator());
@@ -16438,7 +16438,7 @@ ConstraintSystem::simplifyConstraint(const Constraint &constraint) {
     return simplifyValueWitnessConstraint(
         constraint.getKind(), constraint.getFirstType(),
         constraint.getRequirement(), constraint.getSecondType(),
-        constraint.getMemberUseDC(), constraint.getFunctionRefInfo(),
+        constraint.getDeclContext(), constraint.getFunctionRefInfo(),
         /*flags*/ std::nullopt, constraint.getLocator());
 
   case ConstraintKind::Defaultable: